1. Field of the Invention:
The present invention relates to a rubber composition based on hydrocarbon rubber which exhibits improved processability over hydrocarbon rubber used alone but has no bad influence on the physical properties and heat resistance of its vulcanizate.
2. Description of the Prior Art:
Hydrocarbon rubber has some disadvantages. That is, it is insufficient in adhesion, it has an excessively high viscosity, it winds around the roll during processing, and it gives a vulcanizate poor in adhesion.
A common practice to cope with this situation has been to incorporate the hydrocarbon rubber with a tackifier, which includes coumarone resin, phenolic resin, petroleum resin, terpene resin, and rosin derivative.
Although a tackifier improves hydrocarbon rubber in processability, it adversely affects the vulcanizate in physical properties and heat resistance. Moreover, there is a knotty problem that a tackifier hinders crosslinking with a peroxide (which is often used for EPDM).
The present invention was completed to solve the above-mentioned problem. It is an object of the present invention to provide a rubber composition based on hydrocarbon rubber which exhibits improved processability over hydrocarbon rubber used alone but has no bad influence on the physical properties and heat resistance of its vulcanizate.
In order to solve the above-mentioned problem, the present inventors carried out a series of researches which led to the finding that a rubber composition based on hydrocarbon rubber exhibits improved processability over hydrocarbon rubber used alone but has no bad influence on the physical properties and heat resistance of its vulcanizate, if it is incorporated with a specific resin as a tackifier. The present invention is based on this finding.